Trimethoxypropylsilane

Repeated dose toxicity: oral

Administrative data

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

19.11.2003 to 19.05.2005

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2005

Report date:

2005

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: USEPA OPPTS 870.3650

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Trimethoxy(methyl)silane

EC Number:

214-685-0

EC Name:

Trimethoxy(methyl)silane

Cas Number:

1185-55-3

Molecular formula:

C4H12O3Si

IUPAC Name:

Trimethoxy(methyl)silane

Test material form:

liquid

Test animals

Species:

rat

Strain:

other: Crl:CD(SD)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: No data
- Age at study initiation: Nine weeks
- Weight at study initiation: Males: 294.2-351.5; Females: 200.2-260.2 g
- Fasting period before study: None
- Housing: individually housed in suspended wire-mesh cages (pregnant rats in shoebox cages)
- Diet (e.g. ad libitum): Ad libitum (except during FOB)
- Water (e.g. ad libitum): Ad libitum (except during FOB)
- Acclimation period: Six days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20.2-22.5
- Humidity (%): 36.0-62.0
- Air changes (per hr): 10-15
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 09.02.2004 To: 19.04.2005

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS: Conducted over nitrogen atmopshere. Test substance was placed into a volumetric flask and corn oil added to achieve the desired volume. The weight of the test substance added to the flask was used to calculate nominal dose solution concentrations. Dosing solutions were prepared at least once every two weeks consistent with the previously determined 15-day stability. The concentration, homogeneity and stability of the test substance in vehicle for at least 15 days.

VEHICLE
- Justification for use and choice of vehicle (if other than water): No data
- Concentration in vehicle: Various
- Amount of vehicle (if gavage): Up to 3 ml/kg
- Lot/batch no. (if required): 122K0131
- Purity: Considered 100%

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The concentration of methyltrimethoxysilane (MTMS) in corn oil dosing solutions was determined prior to the beginning of the definitive study.

Duration of treatment / exposure:

Toxicity group females and males were treated for 28 and 29 days, respectively. Reproductive group females were treated for 14 days prior to the mating period, during the mating period, and then up to and including post partum day 3, for a total of up to 51 days.

Frequency of treatment:

Daily, seven days/week

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/kg bw/day (actual dose received)

Remarks:

Corn oil

Doses / concentrations 2

Dose / conc.:

50 mg/kg bw/day (actual dose received)

Doses / concentrations 3

Dose / conc.:

250 mg/kg bw/day (actual dose received)

Doses / concentrations 4

Dose / conc.:

1 000 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

10

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Based on a range-finding study
- Rationale for animal assignment (if not random): Weight stratified randomisation process
- Rationale for selecting satellite groups: According to OECD TG 422
- Post-exposure recovery period in satellite groups: None

Examinations

Observations and examinations performed and frequency:

Mortality/Morbidity: Animals were observed at least twice daily in their cages for moribundity and mortality throughout the in-life phase of the study.

Daily Observations: General clinical examinations were made at lease once a day and were conducted immediately after dosing. The examinations included, but were not limited to, changes in the skin, fur, eyes, mucous membranes, respiratory, circulatory, autonomic and central nervous system functions, motor activity and behavior patterns. Findings were recorded for individual animals. General clinical examinations were not performed on days when detailed physical examinations were performed.

Detailed Physical Examinations: All animals received a detailed physical examination once before the first dose administration (to allow for within-subject comparisons), and weekly thereafter. Examinations were made outside the home cage in a standard arena at approximately the same time each day. Observations were detailed and carefully recorded. Examinations included, but were not limited to, changes in skin, fur eyes, mucous membranes, occurrence of secretions and excretions, and autonomic activity. Changes in gait, posture and response to handling as well as the presence of clonic or tonic movement, stereotypies, difficult or prolonged parturition or bizarre behavior were recorded. The presence or absence of findings was recorded for individual animals.

Body weights and food consumption were recorded weekly. Additional body weights for reproductive group females were obtained on gestational day 0, 7, 14, and 20, and within 24 hours of parturition, and on postnatal day 4. Individual food consumption was determined for each group following group specific schedules.

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No

WATER CONSUMPTION: No

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: On day of scheduled termination.
- Anaesthetic used for blood collection: Yes (isoflurane)
- Animals fasted: Yes
- How many animals: Males and toxicity phase females
- Parameters checked in table 1 were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: On day of scheduled termination
- Animals fasted: Yes
- How many animals: Males and toxicity phase females
- Parameters checked in table 1 were examined.

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: prior to the start of dosing and during the  last week of dosing. 
- Dose groups that were examined: adult males and  all toxicity group females
- Battery of functions tested: Unusual body movements, abnormal behaviour and/or posture, and resistence to removal, palperal closure, lacrimation, pupil size, pupil reactivity, salivation, muscle tone, extensor thrust response, reactivity to handling, level of ambulatory activity including rearing, responsiveness to sharp noise, touch, tail pinch, gait evaluation and quantity of urine and fecal pellets voided, behavior, skin or hair coat, respiration, muscle movements, eyes, urine or feces, soiling, general abnormalities and posture, rectal temperature, hindlimb/forelimb grip strength and landing foot splay. Motor activity assessment involved obtaining baseline motor activity data prior to the first dose administration to assist in evaluating potential treatment-related effects by allowing each rat to act as its own control.

Sacrifice and pathology:

Males and toxicity group females were sacrificed after they had been  treated for 28 days.  Reproductive group females and pups were sacrificed  
on day 4 postpartum.  Complete necropsies were performed on the males and the toxicity group females and selected organs were weighed (adrenals, brain, heart, kidneys, liver, lungs, spleen, thymus, uterus, ovaries, testes, prostate, seminal vesicles, and epididymides). Microscopic examination was performed on protocol-specified tissues from all animals in the control and high dose group males and toxicity group females. Microscopic examination of the liver, thyroid, jejunum and duodenum was extended to males and toxicity group females in the 50 and 250 mg/kg dose groups. In addition, the adrenal gland from these middle dose groups was evaluated for the toxicity group females.

Statistics:

All data analyses were carried out using SAS version 8.2. Statistically significant probabilities were reported for /-values of <0.05, <0.02 and <0.01.

Body weight, body weight changes, organ weight, organ to body weight ratios, food consumption, hematology data, clinical chemistry and prothrombin times were analyzed using a one-way Analysis of Variance (ANOVA) if the data satisfied the requirements of normality of the residuals and homogeneity of variance as determined using the Shapiro-Wilk test for normality and Levene’s test for homogeneity of variance. If the data did not satisfy the parametric requirements, a Kruskal-Wallis test was used. If the ANOVA or Kruskal-Wallis test was significant, pair-wise comparisons of the dosed groups to control were made using the Dunnett’s Test or a Wilcoxon test, respectively.

The red blood morphology findings in the hematology data that were reported by severity grade; polychromasia, anisocytes, poikilocytosis, and ananthocytes were analyzed using a Cochran-Armitage trend test to indicate an increasing incidence trend regardless of grade with Fisher’s Exact tests used to indicate increased incidence (non-grade specific) over the control. To determine shifts in severity, analysis using the Kruskal-Wallis test was performed on the graded data only if there was at least once incidence of severity grade seen in the controls group. If the overall Kruskall-Wallis test was significant, pair wise comparisons of the graded animals between the control and treated groups was done using the Kruskal-Wallis.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Clinical signs included transient inactivity or salivation following dosing.

Mortality:

mortality observed, treatment-related

Description (incidence):

There were two unscheduled deaths (one female each at 0 and 50 mg/kg  bw/day); both were related to dosing errors.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Statistically significant decreases in body weight gain were noted for 1000 mg/kg bw/day group males. 

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

Statistically significant decreases in food consumption were noted for 1000 mg/kg bw/day group males. 

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

A marked increase in prothrombin time was observed for males at 250 and 1000 mg/kg bw/day whereas females were unaffected. Exposure was also associated with increased blood platelet concentration for males and females, and increased red blood cell concentration in males at 1000 mg/kg bw/day.

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not examined

Behaviour (functional findings):

no effects observed

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

Increased liver weight was observed for male and female animals at 250 and 1000 mg/kg bw/day.

Gross pathological findings:

no effects observed

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Exposure to MTMS was associated with histomorphological changes in males (liver, thymus, thyroid, duodenum, jejunum) and females (liver, thyroid, duodenum, jejunum, and adrenal gland) at dose levels at or above 250 mg/kg bw/day. 

Histopathological findings: neoplastic:

not examined

Effect levels

Key result

Dose descriptor:

NOAEL

Effect level:

50 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

histopathology: non-neoplastic

organ weights and organ / body weight ratios

Target system / organ toxicity

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

250 mg/kg bw/day (actual dose received)

System:

other: hepatobiliary; gastrointestinal; endocrine; immune system

Organ:

adrenal glands

duodenum

jejunum

liver

thymus

thyroid gland

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

not specified

Any other information on results incl. tables

Toxic Response/Effects by Dose Level:

50 mg/kg bw/day Methyltrimethoxysilane:
Males: None
Females:  None

250 mg/kg bw/day Methyltrimethoxysilane:
Males: 
Increased liver weight (absolute(relative): 19%* (25%*)
Thyroid gland follicular cell hyperplasia/hypertrophy: (incidence 6*/10)
Decreased thymus weight (absolute(relative): 28%*(24%*)
Increased prothrombin time: 2-fold*

Females:
Increased liver weight (absolute(relative): 37%* (41%*)
Centrilobular hepatocellular hypertrophy (incidence 5*/10)
Periportal vacuolation (incidence 10*/10)
Thyroid gland follicular cell hyperplasia/hypertrophy:
(incidence 10*/10)

1000 mg/kg bw/day Methyltrimethoxysilane:
Males:  
Increased liver weight (absolute(relative): 33%* (47%*) 
Diffuse hepatocellular hypertrophy (incidence 10*/10)
Thyroid gland follicular cell hyperplasia/hypertrophy: (incidence 10*/10)
Mucosal lipidosis: duodenum  (incidence 4*/10)
Mucosal lipidosis: jejunum (incidence 7*/10)
Decreased thymus weight (absolute(relative): 35%*(29%*)
Ancanthocytosis (incidence 5*/10)
Increased red blood cell concentration: 16%*
Increased prothrombin time: 2-fold*
Increased serum alanine aminotransferase (48%*)
Increased blood platelet concentration: 16*

Females (Toxicity Phase):
Increased liver weight (absolute(relative)): 197%* (200%*)
Centrilobular hepatocellular hypertrophy (incidence 10*/10)
Periportal vacuolation (incidence 8*/10)
Thyroid gland follicular cell hyperplasia/hypertrophy:(incidence 10*/10)
Adrenal gland hyperplasia/hypertrophy (incidence 10*/10)
Adrenal gland apoptosis (incidence 9*/10)
Adrenal gland lymphocytic infiltration: zona reticularis:(incidence 5*/10)
Mucosal lipidosis: duodenum  (incidence 5*/10)
Mucosal lipidosis: jejunum (incidence 5*/10)

Ancanthocytosis (incidence 4*/10)

Increased blood platelet concentration: 21%*

Where "*" denotes statistically different from control (p<0.05)

Applicant's summary and conclusion

Conclusions:

In the key Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test with trimethoxy(methyl)silane (CAS 1185-55-3), conducted according to OECD Test Guideline 422 and in compliance with GLP, the NOAEL for systemic effects was concluded to be 50 mg/kg bw/day based on organ weight and/or histomorphological changes in males (liver, thymus, thyroid, duodenum, jejunum, and red blood cell) and females (liver, thyroid, duodenum, jejunum, and adrenal gland) at dose levels at or above 250 mg/kg bw/day. In addition, a marked increase in prothrombin time was observed for males at 250 and 1000 mg/kg bw/day whereas females were unaffected, and exposure was associated with increased blood platelet concentration for males and females at 1000 mg/kg bw/day.